High dielectric material and method of making same



Patented June 18, 1946 UNITED HIGH DIELECTRIC MATERIAL AND METHOD OFMAKING SAlVIE Eugene Wainer, Niagara Falls, N. Y., assignor to TheTitanium Alloy Manufacturing Company, New York, N. Y., a corporation ofMaine No Drawing.

Original application June 11, 1943,

Serial No. 490,485. Divided and this application June 21, 1944, SerialNo. 541,475

4 Claims. 1

The present invention relates to ceramic dielectric materials and tomethods of making the same. More particularly, the invention relates tosuch materials in which compounds of titania as the predominatingconstituent are used in combination with compounds of tin.

This is a division of Serial No. 490,485, filed June 11, 1943. Incopending applications for patent, Ser. No. 465,387, filed November 12,1942, and Ser. No. 482,613, filed April 10, 1943, the useful propertiesof barium titanate-strontium titanate mixtures are described. Thepresent inven tion relates to another group of bodies whose usefulnessis equally widespread, in that this group of ceramic compositions hasproperties such as to make them useful as capacitors in radio,television and communications generally, as capacitative temperaturecompensating devices in receivers and communication equipment to preventdistortions due to changes in circuit characteristics caused bytemperature changes. The dielectric constants of ,some of thesecompositions are so high that their utilization in low frequencydistribution and communication systerns such as 60 cycle lines, by meansof capacitative coupling between a low frequency to 120 cycle) hightension transmission line and communication telephone line, is madepossible.

Further, the very high dielectric constants of the ceramic compositionof the present invention make possible the use of these materials aselectro-mechanical devices, for example the transfer of mechanicalenergy or motion into electrical energy or vice versa, in a fashionsimilar to the action exhibited by piezoelectric crystals. Thus I mynovel compositions have possible utility in piezoelectricity,Supersonics, crystal or condenser microphones, frequency stabilizers,loud speakers, phonograph pickups, telephone design, and oscillatordesigns generally. The foregoing remarks apply particularly to thosebodies whose dielectnc constants are over 1000 at radio frequency. Incondenser microphones, very thin sheets of the higher dielectricconstant materials are rigidly clamped at either the center or edges andused as the vibrating diaphragm. The minute changes of position ordimension of the dielectric due to vibration will occasion relativelylarge changes in capacity by means of which sound is transformed intoelectrical energy.

Other members of this group, particularly those having dielectricconstants over 1000 exhibit electrical and mechanical characteristics ofthe same nature as piezoelectrical and pyroelectrical crystals. Forexample, a rod of the material having one end fixed and one end free tovibrate will when in vibration, develop a potential difference ofseveral volts between the two ends of the rod.

The particular usefulness of members of this group as compensators forcorrection of frequency drift, lies not only in the possibility ofobtention of both positive and negative temperature coefficients of awide variety, but also the possibility of controlling the degree ofvariation through choice of the proper composition. These properties,coupled with extremely low power factors in some cases, afford a highdegree of usefulness for this latter class of application.

In general, the novel compositions of the present invention comprisefired mixtures of the titanates and stannates of the alkaline earthmetals. In a broad sense these mixtures may consist of one or moretitanates with one or more stannates. While the alkaline earth metalcompounds generally are of utility in the present invention, those ofparticular importance are the stannates and titanates of barium,strontium and calcium. In general the total stannate content of theceramic body will not exceed 50%. The general classes of compositionscovered by this invention are indicated in the examples. The peculiarlybeneficial effect of the stannate additions is most strikingly shown inthe case of such additions to barium titanate. At radio frequenciesbarium titanate has a dielectric constant of 1200-1300, and atemperature coeflicient which is first negative, then strongly positive,and finally strongly negative between 20 C. and C. Not only may thiserratic behavior be eliminated by addition of the stannates butdielectric constants at least as high as 13000 at radio frequencies arepossible.

In the practice of the invention the ingredients as indicated in thetable below are properly reacted ceramically and then ground so that thecoarsest patricles will pass a 325 mesh screen. The dried powders arethen mixed within the limits indicated by the proportions given in thetable. Approximately 10% water is added and thoroughly mixed in and thedamp powder granulated by passage through a 20 mesh screen. The granulesare then pressed in a die under a pressure of 5 to 10 tons per squareinch, and then allowed to air dry for 24 hours. The pieces used forpurposes of test were roughly 1 inch in diameter and 0.1 inch thick.Pieces of such size were fired on a schedule of 400 F. per hour to thepeak temperature, then held at peak temperature for three hours and thenallowed to cool. The maturation temperature for all the bodies listedbelow is between 2450 and 2500" F. After cooling Table III.-BaT!zO3series the opposing parallel surfaces are painted with silver powderpaste which is fixed as a silver elec- One mcgacyclo One kllocyclc Otrade by firing to 1500 F. Comp tumor The values obtained below weredetermined at 5 N0, gmnnatg Diem Power melee Power one megacycle using aradio frequency bridge of constant i g g constant ag ns standard design.Resistivity was determined on a high sensitivity resistance circuit onwhich a 1 100 +1 BaSnOa" L525 0,820 17500 M resistance of a milllonmegohms could easily be 2 100 5 a sno u 2,010 1.100 2,155 1.0 :1 10008m 1. 3.530 2.730 3, 070 1.4 detected, the zero point indicator belng agal 10 4 SOHOBQSHO" 4,175 M70 7275 0.01 vanometer. The 1000 cyclemeasurements were 5 55+35 Bastion. 570 0.420 033 0.03

- 5 50+50 Basile... 253 0.200 230 2.5 obtained through use of animpedance bridge of 7 100 +1 srsnohfl 1,650 0.950 1' 730 L1 standarddesign, whose arms were resistive coma 100+5 srsnolm 2,300 1.500 2,4701.5 ponents I og o s sx oa. 4,300 0. 030 4, 7 2.3

0 r n 1,720 0.320 1, 0. Having described the method of practice of the11, 05+25 srsnogm 503 0,230 505 0.05

l2. 50+50 SrSnO. 272 0.180 276 l. 6 invention, the following sets oi.tables indicate 100 +1 oasnda" mm 1.100 L790 M the type of compositionsand the values obtained 14 .05 Casio, 2,580 2 0 2,340 1.3 thereon. s.500 goo 1 1, 41 1 1 The peculiar advantage of such compositions as 2 1 31 capacitor materials for by-pass and filter condens- 010 130 4 2. 8102. 620 3, 290 2. 0 ers may be seen from perusal of the following fig-6,575 2,720 7,060 ures. For example, present day electrolytic 9,450 190010,200 12.500 2.200 13,100 0.4 condensers at best have power factorsbetween 824.18 8 11 50 1.000 7,250 0.1 6.0% and 18.0% whereas all thevalues in the table are below 3.0%. Thus such materials may 25 Table 1V.-Comple:c series be used as substitutes for paper and electrolytics.Bodies having power factors below 0.1% are suit- Onemegacycle Onekiloc'yclo able as substitutes for mica capacitors. The possi- C ombility of variation and control of temperature coef- Composition BMW mD181 fower flcients, thus making available these compositions oonpepoonas compensator compositions. is indicated from mm cent cent the datagiven in Table V and following. These temperature coemcients weremeasured at one 1 s0 B2100, 1013551110.-- 4,150 0. 05 3, 510 0.01mega'cycle- 2 i a n 'r 'l 20 1103110, 1 400 0. 3s 1. 415 0.01

Table I.CaTiO1 series 10 3:13:10.

3 Z Bas'Ilg; 10 13231101.. 2,105 0.50 1,805 0.02

11 a One megacycle One kilocycle 4 5 8: 1- 1,475 1,450

l 11 3 Comp. CaTi0;-etan- 5 85 Ba'ilO; 5BaSnO; 7,72) 1. 74 8,100 0.50

No. natc Dielec Power Dielec Power 5 BIBHO: 5 s i fF tor 1m 40 5 70115210, 10 BaSnO 1,350 0.21 1,320 0.20 can! u percent cons n pem nt 10SIBDO: 10 Si'TiOs 16 SrSnO; l5 Sr1i0 11%; %S8"- 12% 3818 i5 i a n 1. 5.3 10o+10 B38110]. 148 0.010 151 1.3 T ble V--TemPerature ca city d aJ32 3?8' 12 8'81? 3 i a n 2 l4 .3 50+50 BaSn0 133 0.015 140 1.4 a Body#3, Bod 00.1.1 g L" 5 01 155 1.4 Temperature, C. CaTlOz CB 10; O8 101100+5 BrSn0|.- 133 0.010 143 1. 4 series W125 W168 100+10 SrSnO| 1320.010 137 1.4 s0+2o 1115110,--- 107 0. 010 123 1. 4 c5+35 Branch... 770. 010 35 1. 7 K K K +50 srsnoi-.. 57 0.030 73 2.5 148 137 132 100+1045110." 150 0. 010 157 1. 4 143 137 100+5 05511101.. 145 0.010 153 1.3143 131 10o+10 05550.. 132 0. 010 142 1.4 147 136 131 30-4-20 CsSn 1..103 0. 010 117 1.4 146 135 +35 055110... 0. 010 35 2.1 kg 1: 1a....50+50 055501-. 01 0.010 72 1.3 m m 128 iii 13? 1% Table IIr-S' series 14I 23 it; it One megacycle One kilocycle 131 1% 1n Comp. SrIiOr- No.stannate Dielec' 2127:: Dielec' forget Table VI.--Temperature capacitydata DO I constant percent constant percent I B511 #3, Bod m,Tempcrature,0. Br 10, s 0. who, 100+1 13281101.. 240 0. 010 250 1. 1series series lurid 100+5 BaSnO1. 247 0. 010 240 1.0 10o+10 BBSHOL 2100. 010 220 1.7 233 0.010 217 1.2 K K K 155 0.040 153 1.0 210 215 20s 900.030 07 1.5 210 215 205 242 0. 040 244 1.2 205 215 207 227 0.000 2351.2 207 5 213 200 215 0.030 217 1.2 205 212 205 144 0. 010 1. 7 203 210203 75 0. 010 34 2.0 201 205 202 45 0.030 52 8.0 103 205 100 247 0.030251 1.1 100 205 m 1o0+5 CaSn01. 237 0. 040 244 1.1 103 204 104 1oo+1o0151101. 203 0.020 214 1.1 130 202 101 a0+20 048110... 141 0.010 145 1.3135 200 13! 55+35 c5550... 27 0. 010 10s 2. 5 134 195 154 50+50 CaSnO1.-75 0. 010 85 1.5 105 152 Table VIL-Temperature capacity series Body #3,Body #9, Body #15, Body #5, Temperature, C. BBTIO] BeTiOi BaTiOi Complexseries series series series The temperature coefllcients of thecompositions covered in Tables V, VI and VB are indicative of the scopeof variation possible. While. single compositions may yield the desired6 coefllcient, an infinite variety of coemcient is possible throughparallel combination 01' one or more bodies.

From the foregoing it will be seen that the present invention providescompositions eminently suitable as dielectric materials in a widevariety of uses. The above examples have been set forth as illustrativeof the invention, the scope thereof being comprehended within theappended claims as it will be apparent that wide variation may be hadfrom the specific examples.

What is claimed is:

1. A ceramic composition which comprises calcium titanate and analkaline earth stannate.

2. A ceramic composition which comprises calcium titanate and calciumstannate.

3. A ceramic composition which comprises calcium titanate and strontiumstannate.

4. A ceramic composition which comprises calcium titanate and bariumstannate.

' EUGENE WAINER.

